This invention relates to a system for disposal of aqueous sewage sludge by using it to make cement. Recently, amounts of sewage sludge released mainly from waste water treatment plants are increasing year by year, and are being treated by various processes.
For example, sewage sludge is mixed with fermentation auxiliaries, such as rice hulls and saw dust, and subjected to fermentation to produce compost. This compost is used for farmland, but its consumption is limited in quantity, and it is difficult to consume and reduce large amounts of compost.
Another method is to throw untreated sewage sludge into the seas. But regulations are gradually becoming stricter and this method is not desirable in view of the need for protection of the environment. Another method is to spread the sludge on farmland expecting fertilizing effects, but it is difficult to dispose of large amounts by this method.
Untreated sewage sludge is used in land reclamation, or sewage sludge is solidified with a solidification agent such as cement or lime and used in reclamation. However, it is becoming difficult year by year to find lands to be reclaimed; thus limiting the disposable amounts.
Sewage sludge has been burned in order to reduce the volume. However, this method releases large amounts of ash, which are usually disposed of by reclamation and hence the disposable amounts are limited. Part of the ash is used in architectural and horticultural materials, but amounts of consumption in these areas are also limited. Furthermore, this method has the inherent problem of high combustion costs.